1. Field of the Invention
The present invention relates to an imaging apparatus provided with an imaging unit including a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor in which plural light receiving elements are arranged in a matrix, and a method for correcting defective pixels included in an image picked up by the imaging apparatus.
2. Description of the Related Art
In a semiconductor wafer process for manufacturing a CCD image sensor or a CMOS image sensor in which photodiodes (light receiving elements) are arranged in an array, point defects (a defect in a light receiving element at a particular point) and/or line defects (a defect in a light receiving element in a particular line) are often caused by particles generated during the process. These defects increase as the chip size of the image sensor is enlarged and/or intervals between the light receiving elements are reduced.
When there is a point defect or a line defect, a portion corresponding to the defect in an image will not be output properly, thus producing a defective pixel. Accordingly, there has been proposed a method of correcting a defective pixel in an image output from an image sensor, which defective pixel is caused by a point defect or a line defect. Specifically, the defective pixel is corrected according to an adjacent pixel or image information of an adjacent line of light receiving elements. In this method, the defective position is searched for and saved into a ROM in advance. The defective pixel, which is generated when an image of the imaging object is picked up, is corrected according to pixel information surrounding the defective pixel. Then, the corrected image is output.
Another defective pixel correcting method is proposed, in which the defective pixel is corrected without saving the defective position into a ROM (see, for example, Patent Document 1). In this method, a determining circuit is provided for determining whether a target pixel is a defective pixel. In the event that the determining circuit determines that the target pixel is a defective pixel, the target pixel is corrected according to pixel information surrounding the target pixel.
Patent Document 1: Japanese Laid-Open Patent Application No. 2004-112736
In both of the above-described defective pixel correcting methods, the image with the corrected defective pixel is an artificial (pseudo) image, and is thus not exactly the same as the actual image. Specifically, the quality of the image is degraded where the defective pixel has been corrected. For this reason, the number of defects which leads to degraded image quality is included among factors determining the product quality of an image sensor. Therefore, if there are many point defects and/or line defects, the image sensor will not be able to pass a product quality test, which reduces product yield.